There have been many ways sought to detect key movement on pianos and keyboards. Electronic keyboards have the advantage of building in key detecting devices during its design and manufacturing. However, some older electronic keyboards, organs, and pianos are not equipped with key detecting devices and circuitry. Pianos can be retrofitted with sensor units underneath the piano keyboard, and there are retrofit systems that operate using different technologies. One of these technologies uses optical couplers to detect or monitor the activity of the key. Many applications use the optical coupler principle to monitor key activity from beneath the key while others monitor the key activity from atop the keyboard.
Patents U.S. Pat. No. 5,567,902, U.S. Pat. No. 5,231,283, and U.S. Pat. No. 5,763,806 use optical sensing from underneath the piano keys to accomplish the detection of black and white key movements. None of these however have addressed optically sensing the black and white keys from the top of the keys. It would be desirable to have a portable key detection apparatus for over the top of the keys.
U.S. Pat. No. 5,394,784 discloses an apparatus seemingly attached to the topside of the keyboard. However, its objective is to display key information with visual LEDs. It assumes that the keyboard it rests on has the capability of detecting key movement. It would be desirable not to rely on the piano""s or keyboard""s capability, but to independently provide the capability of detecting key movement.
U.S. Pat. No. 4,448,103 discloses an apparatus that rest over the top of the piano keys. By its nature and principle of operation, it is bulky, and it would most notably be difficult to provide an effective way to mount and stabilize the housing. The invention chooses to describe mounting xe2x80x9cby any appropriate means such as a bracket, adhesives or adhesive tape, screws or bolts, etc.xe2x80x9d It would be desirable to have a thin, light weight, unobtrusive apparatus without additional bulky, unattractive end pieces and procedures. It would be desirable to stabilize the device in a suitable, simple, and effective manner.
U.S. Pat. No. 4,790,230, discloses a keyboard device that is mounted on top of a keyboard and uses optical sensing for detecting key movement. However, while the invention is suitable for detecting white key movement, it is inadequate to accurately detect and transmit black key movement due to inadequate amounts of reflected signals from the black keys.
Further, U.S. Pat. No. 4,790,230 states that to compensate for the black key""s color, each black key""s optical emitter signal strength can be increased. However, this introduces stray reflected light that would interfere between adjacent white keys. Unless a means is provided to shroud or block the adjacent stray light interference, the invention""s goal of treating all keys alike is inadequate and unsuitable. It would be desirable to avoid special operational treatment of signal strengths due to the significant difference between the black key and white key reflectivity. Rather, it would be desirable to simply increase the reflective properties associated with of the black key movement.
Accordingly, it is a primary object of the present invention to provide a portable, lightweight, and unobtrusive apparatus for detecting piano/keyboard key movement that compensates for the deficiency of the black key reflective properties.
It is another object of the present invention to disclose means to apply thin, reflective, flexible inserts that position themselves between their respective black key and optical device.
It is another object of the present invention to provide a simple attachment means utilizing the mechanical design of the device to easily mount and provide stability in the detection of piano key movement.
The goal of the present invention is to provide a modular and portable means to detect key movement and velocity on virtually any available piano or keyboard. A device such as this would enhance and enrich performances, compositions, and piano keyboard training given the sophisticated computer programs and sound hardware available. The present invention is installed between the black keys and fallboard or keyboard casing, spanning any number of keys or octaves up to the full length of a keyboard. Interconnecting circuitry contained in the invention attaches to a local or internal processor unit. The processor unit analyzes and converts the detected key movements into a format suitable for further transmission to a computer or musical device sharing the same protocol and physical interface such as MIDI.
The present invention uses one optical transmissive coupler per key. Each optical transmissive coupler, or optocoupler, has an emitter and phototransistor. The optocoupler, detects key movement by generating a light signal from its emitter and detecting the reflected signal from the key with its phototransistor. The white key optocoupler is positioned near the white key. The emitter signal is reflected off the white key and detected by the phototransistor. The black key optocoupler is positioned near the black key. Since the emitter signal reflected off the black key is too weak for accurate detection of the black key movement by the phototransistor, each black key is equipped with a reflective insert. There are two types of reflective inserts to be described: vertical flaps and horizontal drapes. The inserts move or glide with the black key movement. The emitter signal is now reflected off the reflective insert and detected by the phototransistor.
The present invention takes advantage of the inconspicuous narrow gap between the back of the black keys and piano fallboard or electronic keyboard casing. The rectangular design of the back side of the present invention provides an ideal mounting means between the black keys and the piano fallboard or musical keyboard casing. The snug fit eliminates the need for end-mounting hardware and provides stability during use. If the gap between the black keys and the fallboad are wider than normal, additional rectangular strips of varying thickness can be installed behind the backside cover to keep the present invention firmly in place.